The present invention relates to a device for generating images (hereafter, called xe2x80x9cvirtual imagesxe2x80x9d,) in a virtually defined space (hereafter, called xe2x80x9cvirtual spacexe2x80x9d), and more particularly, to technology for providing a highly realistic representation of objects made of a pliable material which are liable to the effect of external forces, for instance, loose portions of clothing, hair, cloth, cords, sashes, and the like.
With the progress in computer graphics,(CG) technology, it has become possible to represent images of a virtually defined world, three-dimensionally and in real time. In the field of video game device technology, central processing units (CPU) capable of high-speed calculation and video display processors (VDP), which have been developed in recent years, are installed in game devices and this computer graphics technology is used economically and at high-speed.
In a video game device of this kind, it is necessary to move a display object quickly and freely within a virtual space, in order to change the contents of the game continuously on the basis of the user""s operations. For this purpose, usually, a polyhedron is formed by dividing a display object, such as a character (person) or the like, into triangular or quadrilateral polygonal fragments, known as polygons, and the spatial positions of each of the polygons are changed simultaneously, thereby representing movement of the polyhedron, in other words, the display object. Furthermore, if specific parts or surfaces of the display object, such as the character""s arms or legs, perform the same movement, then a polygon data group (polyhedron) wherein a plurality of polygons are collected is taken as a single unit, a spatial position is given for each polygon data group, and the specific parts or surfaces are moved simultaneously.
Whatever method is adopted, provided that the display object is a rigid object, an animated image can be generated with suitable illustrative quality by taking the polygons as display units.
However, if the polygons are taken as fixed display units, as in conventional video game devices, a problem arises in that the illustrative quality is insufficient when a polyhedron forming a pliable, planar display object is displayed.
A conceivable method in a case where, for example, billowing movement of a polyhedron of this kind, such as cloth or hair, is represented, is a method whereby the positional coordinates of the apexes of polygons in a virtual space are determined successively by a program each time the display screen is renewed, in other words, a method known as polygon pattern change. However, materials which are pliable and light, such as hair, or the like, change shape readily and in a complex manner under the effect of external forces. Therefore, in a situation where the state of the screen and the characters changes frequently, as in a video game, it is practically impossible to predict all the external forces which may act on a character""s hair, or the like, and the corresponding movements thereof, or to run a program which can manage these movements.
A further conceivable method is to calculate spatial coordinates in a virtual space by setting up simple equations for the apexes of each polygon. However, using simple equations alone, it is difficult to incorporate into the equation the effect of gravitation on movement, and furthermore, a huge volume of calculations is involved and processing inevitably becomes slower.
In view of the foregoing, it is an object of the present invention to provide a game device capable of providing a highly expressive display of a polyhedron.
In other words, it is a first object of the present invention to provide an image generating device whereby a highly realistic representation of a display object consisting of a pliable material can be obtained.
It is a second object of the present invention to provide an image generating method whereby a highly realistic representation of a display object consisting of a pliable material can be obtained.
It is a third object of the present invention to provide a recording medium on which an image generating method, whereby a highly realistic representation of a display object consisting of a pliable material can be obtained, is recorded.
In an image generating device which displays images of display objects located in a virtual space, the invention according to claim 1 is an image generating device comprising:a mass point setting circuit for setting mass points on the display object; an influential force setting circuit for setting influential forces acting on the mass points; a mass point position calculating circuit for calculating the positional coordinates of the mass points on the basis of the influential forces set by the influential force setting means; and a figure generating circuit for generating a prescribed figure comprising the display object on the basis of the positional coordinates of the mass points calculated by the mass point position calculating circuit.
The invention according to claim 2 is an image generating device according to claim 1, wherein the mass point position calculating circuit takes at least one of the mass points as a reference point and calculates the positional coordinates of the mass points in order of their proximity to the reference point, starting from the reference point.
The invention according to claim 3 is an image generating device according to claim 1, wherein the influential force setting circuit sets tensile forces acting between the mass point and mass points adjacent to this mass point as influential forces acting on the mass point.
The invention according to claim 4 is an image generating device according to claim 1, wherein the influential force setting circuit sets a wind force acting on the mass point as an influential force acting on the mass point.
The invention according to claim 5 is an image generating device according to claim 1, wherein the influential force setting circuit sets the stress acting between the mass point and mass points adjacent to this mass point as an influential force acting on the mass point.
The invention according to claim 6 is an image generating device according to claim 1, wherein the influential force setting circuit sets the gravitation acting on the mass point as an influential force acting on the mass point.
The invention according to claim 7 is an image generating device according to claim 1, wherein the influential force setting circuit sets the force of inertia acting so as to maintain the distance between the mass point and a mass point adjacent to this mass point at a uniform distance, as an influential force acting on the mass point.
The invention according to claim 8 is an image generating device according to claim 7, wherein the influential force setting circuit sets the force of inertia required in order to move the mass point from the position of this mass point as calculated assuming that there is no force for maintaining the distance between the mass point and a mass point adjacent to this mass point at a uniform distance, to a position as calculated by incorporating the force, as the influential force.
The invention according to claim 9 is an image generating device according to claim 1, wherein the influential force setting circuit sets the influential forces acting between a prescribed mass point and mass points adjacent to this mass point as ineffective forces.
The invention according to claim 10 is an image generating device according to claim 1, wherein, when the displacement of the mass point is greater than a specific threshold value, the mass point position calculating circuit calculates a value obtained by multiplying the displacement by a coefficient k (0 less than k less than 1) as the displacement of this mass point.
The invention according to claim 11 is an image generating device according to claim 1, wherein the figure generating circuit generates a figure using the positional coordinates of the mass points, wherein prescribed internal angles of the polyhedron forming the display object are maintained below a prescribed value.
The invention according to claim 12 is an image generating device according to claim 1, wherein the figure generating circuit successively links adjoining mass points in one direction of the display object by means of a wire-shaped figure, and generates an overall image wherein wire-shaped figures are arranged alongside each other.
The invention according to claim 13 is an image generating device according to claim 1, wherein the figure generating circuit generates a figure of the display object by means of triangular shapes formed by setting diagonals in quadrilateral shapes comprising four mutually adjacent mass points as apexes.
The invention according to claim 14 is an image generating device according to claim 13, wherein, when any of the internal angles of the triangular shapes is equal to or greater than a prescribed angle, the figure generating circuit sets a further diagonal which is different to the diagonal forming one edge of the triangular shapes, and generates a figure of the display object by means of triangular shapes formed by the further diagonal.
In an image generating method for displaying an image of a display object located in a virtual space,the invention according to claim 15 is an image generating method comprising the steps of: setting mass points on the display object; calculating positional coordinates for the mass points on the basis of the values of influential forces acting on the mass points; and generating a prescribed figure comprising the display object on the basis of the calculated positional coordinates of the mass points.
The invention according to claim 16 is an image generating method according to claim 15, whereby, in the step of calculating positional coordinates for the mass points, at least one of the mass points is taken as a reference point, and the positional coordinates of the mass points are calculated in order of proximity to this reference point, starting from the reference point.
The invention according to claim 17 is an image generating method according to claim 15, whereby, in the step of generating the prescribed figure, a figure wherein all internal angles are less than a prescribed angle is generated.
The invention according to claim 18 is an image generating method according to claim 15, wherein the influential forces are the values of tensile forces acting between the mass point and mass points adjacent to this mass point.
The invention according to claim 19 is an image generating method according to claim 15, wherein the influential force is the value of a wind force acting on the mass point.
The invention according to claim 20 is an image generating method according to claim 15, wherein the influential force is the value of a stress acting between the mass point and a mass point adjacent to this mass point.
The invention according to claim 21 is an image generating method according to claim 15, wherein the influential force is the value of a gravitation acting on the mass point.
The invention according to claim 22 is an image generating method according to claim 15, wherein the influential force is the force acting such that the distance between the mass point and a mass point adjacent to the mass point is kept at a uniform distance.
The invention according to claim 23 is an image generating method according to claim 15, wherein the influential force is the force of inertia required in order to move the mass point from the position of this mass point as calculated assuming that there is no force for maintaining the distance between the mass point and a mass point adjacent to this mass point at a uniform distance, to a position as calculated by incorporating the force.
The invention according to claim 24 is an image generating method according to claim 15, wherein the step of calculating positional coordinates for the mass points takes the influential forces acting between a prescribed mass point and mass points adjacent to this mass point as ineffective forces.
The invention according to claim 25 is an image generating method according to claim 15, wherein, when the displacement of the mass point is greater than a specific threshold value, the step of calculating positional coordinates for the mass points takes a value obtained by multiplying the displacement by a coefficient k (0 less than k less than 1) as the displacement of this mass point.
The invention according to claim 26 is an image generating method according to claim 15, wherein the step of generating a prescribed figure generates a figure using the positional coordinates of the mass points, wherein prescribed internal angles of the polyhedron forming the display object are kept below a prescribed value.
The invention according to claim 27 is an image generating device according to claim 15, wherein the step of generating a prescribed figure successively links adjoining mass points in one direction of the display object by means of a wire-shaped figure, and generates an overall image wherein wire-shaped figures are arranged alongside each other.
The invention according to claim 28 is an image generating method according to claim 15, wherein the step of generating a prescribed figure generates a figure of the display object by means of triangular shapes formed by setting diagonals in quadrilateral shapes comprising four mutually adjacent mass points as apexes.
The invention according to claim 29 is an image generating method according to claim 28, wherein, when any of the internal angles of the triangular shapes is equal to or greater than a prescribed angle, the step of generating a prescribed figure sets a further diagonal which is different to the diagonal forming one edge of the triangular shapes, and generates a figure of the display object by means of triangular shapes formed by the further diagonal.
The invention according to claim 30 is a mechanically readable recording medium whereon programs are recorded for implementing an image generating method according to claims 15 to 29 in a computer.